WOn't play video off a My book Live

My WDTV Live has stopped playing videos from my WD MyBook Live video folder. It worked fine until a few days ago. I can see the video folder, and the files inside it but when I try to play one all I get is the little circle going round. If I copy the file to a memory stick, WDTV will play it ok from that, so it’s not a corrupt file. I’ve rebooted everything but that made no diffference. Any ideas?

Are you playing the files via media server or network shares. Can you play music etc OK. What type of video files are they and does it happen with all your video files.